Risk factors for failed induction in nulliparous women

Objective: To identify risk factors for failed induction in nulliparous women. Material and methods: A retrospective cohort study of nulliparous women admitted for induction of labour (IOL). Identification of risk factors for failed IOL by comparing clinical characteristics of patients with a failed IOL defined as birth by caesarean section (LSCS) with those achieving vaginal birth. Results: During a 12 month episode, 400 nulliparous women had an IOL; of these 168 (42%) failed to deliver vaginally. Independent antenatal risk factors for failed IOL were higher maternal age (OR = 1.052 per additional year), being shorter (OR = 1.112 per cm less maternal height) and a lower cervical dilatation score (OR = 1.411 per lower cervical dilatation score). A longer active phase (OR = 1.004 per additional minute) was the only independent intrapartum risk factor for having a LSCS. Conclusions: Maternal age, height and cervical dilatation are independent antepartum risk factors, while duration of active phase is the single independent intrapartum risk factor for a failed IOL. Increased maternal BMI was less of a risk factor than anticipated with increased risk for failed IOL, as independent risk factor, more or less restricted to the morbidly obese women.